The present invention relates generally to a double-row spherical roller bearing including retainers each molded of a synthetic resin. More particularly, the present invention relates to improvement of a double-row spherical roller bearing of the foregoing type.
To facilitate understanding of the present invention, a typical conventional double-row spherical roller bearing including retainers each molded of a synthetic resin will be described below with reference to FIG. 4 and FIG. 5.
FIG. 4 is a fragmentary sectional view of the conventional double-row spherical roller bearing. As shown in the drawing, the spherical roller bearing includes as essential components an inner race 51, an outer race 52, double-rows of spherical rollers 53 located between the inner race 51 and the outer race 52 arranged in the equally spaced relationship in the circumferential direction, and two retainers 55 each molded of a synthetic resin to hold the spherical rollers 53 therein.
As is best seen in FIG. 5, each retainer 55 is constructed such that an annular portion 56 on the large diameter side and an annular portion 57 on the small diameter side are integrally jointed to each other with a plurality of retainer bars 58 each bridged therebetween. With this construction, each spherical roller 53 is rotatably received in a pocket 60 which is defined by both the annular portions 56 and 57 and adjacent retainer bars 58.
A side surface 58A of each retainer bar 58 is formed by a part of the spherical surface extending around the outer peripheral surface of each spherical roller 53. In addition, side surfaces 59A, 59B and 59C of each projection 59 projecting from the retainer bar 58 to come in contact with the spherical roller 53 are likewise formed by a spherical surface corresponding to the peripheral surface of the spherical roller 53. As the spherical roller 53 rolls, it comes in contact with the projection 59 at two points located on the opposite sides of the side surface 59B as seen in the axial direction, whereby disengagement of the spherical roller 53 from the pocket 60 is reliably prevented.
With the conventional double-row spherical roller bearing constructed as described above, each of the side surfaces 59A, 59B and 59C on the projection 59 projecting from the central part of each retainer bar 58 is formed as part of the spherical surface coinciding with the spherical surface of each spherical roller 53. Thus, there arise problems that lubricant hardly penetrates through the gap between the projection 59 and the spherical roller 53, and moreover, it is technically difficult to fabricate a molding die for molding retainers 55 using a synthetic resin.
In addition, the side surface 58A of each retainer bar 58 is formed as part of the three-dimensional curved surface coinciding with the spherical surface of each spherical roller 53 while extending from the end part on the opposite sides of the projection 59 of the inner race 51 side to the end part on the opposite sides of the same on the outer race 52 side, causing a part of the spherical surface of the spherical roller 53 to be closed with the aforementioned end parts on the opposite sides of the projection 59. Thus, there arises another problem that lubricant hardly penetrates through the gap between the side surface 58A of the retainer bar 58 and the spherical surface of the spherical roller 53, resulting in a lubricant film being formed with difficulty.
Further, since the side surface 58A of the retainer bar 58 is formed as a part of the three-dimensional curved surface, it is practically difficult to remove a molded product of each retainer 55 from the molding die for molding retainers 55 using a synthetic resin after completion of each molding operation.